Water Planet Challenge

Investigating The Impact of Choosing High-Efficiency Light Bulbs - Middle School

Introduction

Do you know how much electricity you use daily? Most adults don’t. Students are usually unaware of the amount of electricity they use. Perhaps more importantly, they have little notion of the resources needed to supply that electricity.

It’s a challenge for middle school students to grasp the concept of how electrical energy is transferred from power stations to daily use in the home. For instance, students often think that if you use an electric car you are not using coal, oil or natural gas. This misunderstanding arises because students don’t connect the use of resources with the electricity needed to power the car.

Another misconception is the relative efficiency of devices that use electricity. Students may not understand that energy transfer always results in a loss of energy through heat. They may not understand that such loss of energy is a waste of resources, and a hidden “tax” on our use of energy.

Students also have trouble understanding the consequence of using electricity generated with nonrenewable versus renewable resources. Ask students why renewable resources are a better option than nonrenewables, and they have trouble answering.

This lack of understanding arises because students rarely appreciate the environmental impact of generating electricity. Students might not realize that electricity generated from fossil fuels carries a high environmental cost, particularly compared electricity generated from renewable resources.

This lesson will help students connect the dots. In the lab section, you will guide students to compare energy efficiency of compact fluorescent electric bulbs compared with incandescent bulbs. They will learn that the choice of one bulb over another impacts their home power bill. From this everyday experience, a series of guided questions and fact-finding takes them to the broader consequences of electricity efficiency. In this way, they learn that a choice of one type of light bulb over another does impact the environment, through its influence on demand for electricity. To bring things full circle, the students learn that lowering demand for electricity reduces the need for power stations and increases the likelihood that renewable resources can meet the growing demand for electricity.

Objectives

1. Understand the different ways electricity is produced and how it is used by businesses and individuals
2. Demonstrate that low wattage light bulbs are more efficient and hence sustainable than traditional light bulbs
3. Differentiate between the environmental consequences of using renewable versus nonrenewable resources for electricity production
4. Highlight straightforward and inexpensive changes people can make to reduce their individual demand for electricity

Materials

Materials for research:

• Computer with Internet access
• Library and/or classroom resources

Materials for the inquiry:

• Clamp Lamp

• Ring stand or chair set on counter for clamp lamp to be secured
• Extension cord
• Two different wattage incandescent light bulbs*
• Two different wattage compact fluorescent light bulbs*
• Two different wattage LED light bulbs*
• Thermometer
• Ruler or meter stick
• White piece of tag board or poster board
• Watch or stopwatch

* NOTE: Choose light bulbs of comparable luminosity. The aim is to show that CFLs produce the same amount of light for much less power. For example, a 60W incandescent has the same light output as a 15W CFL. A 100W incandescent has the same light output as a 25W CFL. HINT: If time or budget does not allow for use of four bulbs, you can complete the activity just comparing one incandescent bulb with a CFL bulb

Vocabulary

• Energy– capacity of a system to do work
• Watts – amount of energy used per unit time
• Lumen – amount of light output
• Heat – energy transferred by a temperature difference
• Efficiency – difference between amount of energy put in and energy wasted as heat
• Electricity – energy available from the flow of charge
• Natural resources – things that we use provided by the environment
• Fossil fuels – hydrocarbon compounds formed from organic matter
• Renewable – natural resources renewed by nature over time
• Nonrenewable – natural resources that are not renewed by nature over time

Essential Background for Teacher

This section is need-to-know information for the teacher to teach the lesson effectively.

Key Questions:

• Why should we care about electricity efficiency?
• What is the benefit of using renewable versus nonrenewable resources to generate electricity?
• What are the environmental consequences of electricity production?
• How can we make choices in our daily behavior and use of electricity to reduce electricity demand?
• How can we switch from using nonrenewable resources to renewable sources of electricity generation?

Key facts:

• More than 90 per cent of our electricity is produced using nonrenewable resources. More than three-quarters of our electricity is produced using fossil fuels. Nonrenewable resources will run out, so using them to generate electricity is not sustainable. If we do not switch away from nonrenewable resources our present way of life cannot be continued. Any measure to improve efficiency will lessen demand on nonrenewable resources and help sustain our way of life.
• Use of renewable resources is sustainable since these resources will not run out. By using renewable resources we can sustain our civilization indefinitely. Renewable resources have a smaller “carbon footprint” and so contribute less to global warming than fossil fuel-based nonrenewables.
• Mass production of electricity incurs environmental costs including pollution and land degradation. Fossil fuel plants pollute the atmosphere with carbon dioxide, which contributes to global warming, and sulfur dioxide, which causes acid rain. Nuclear power generation creates radioactive waste that needs special handling procedures and fortified storage facilities. Extraction of fossil and nuclear fuels also incurs a substantial environmental cost through pollution risk and land degradation. The environmental impact of renewable sources of energy is much lower.
• Electricity production can impact on marine ecosystems in several ways. Acid rain runoff can damage fragile ecosystems such as coral reefs. It can cause imbalances in water chemistry of lakes and oceans. Oil spills can devastate marine ecosystems and cause long-term damage to shoreline habitats. Discharge of warm water (a byproduct of cooling systems) can disrupt the ecology around a power station. Although renewable resources are desirable, there is little research on the environmental impact of large tide or wave power installations.
• Daily choices can significantly reduce electricity demand. For example, if you switch a 100W light bulb in your home for a low-energy 100W equivalent, you will save the amount of electricity required to boil 210 liters of water. Over a year, this could save $10 on your electric bill. Since most house have at least 20 electric bulbs, switching to low energy alternatives house-wide could save $200 on the annual electric bill.
• In order to facilitate a switch from nonrenewables to renewable sources of electricity generation, we must first limit demand, or at least the growth of demand. The easiest way to do this is to increase the efficiency with which we use electricity.

General Background for Teacher

This section provides additional information for the teacher who wishes to delve more into the topic.

How we use electricity

Since the Industrial Revolution we have come to rely on electricity for innumerable everyday uses. Businesses use electricity to power industry and manufacturing. In the home we use electricity for numerous labor-saving devices, heating and cooling our homes, cooking food, and entertainment. Without electricity, our civilization would not be possible.

How we generate electricity

Power stations use renewable and nonrenewable natural resources to generate electricity. The primary non-renewable resources are petroleum (or crude oil), coal, and natural gas and nuclear fuels. Fossil fuels are typically recovered by drilling wells, or digging surface and deep mines. They are comprised of organic compounds (hydrocarbons) formed from the remains of plants and animals that lived millions of years ago. Layers of sand and silt covered the dead organic material. Heat and pressure deep beneath Earth’s surface transformed this organic matter into coal, oil and natural gas.

Despite the obvious advantages of using renewable resources to produce electricity, most power stations in the United States use coal, oil, or natural gas. This is primarily due to history and economics. The technology to generate power using fossil fuels was developed first. As the country industrialized, investment was put into these established technologies. At the time, no need was seen for an alternative. Today, we have a legacy of past policies and practices, which are no longer appropriate for a future in which fossil fuels will be increasingly scarce. You can see that legacy in the statistics of our current sources of electric power generation. More than four fifths is generated using fossil fuels. Less than a tenth of the country’s electricity is generated by nuclear power and less than that is generated using renewable resources. In order to prepare for a sustainable future, we must switch to a higher proportion of electricity generation from renewables.

However, there is a “chicken and egg” situation. Proponents of the status quo assert that renewables are unable to meet electricity demand. Without investment in renewables that will always be true. One way out of the conundrum is to reduce demand. The easiest way to do this is to improve energy efficiency.

See attached graph

Nonrenewable versus renewable resources

In the U.S. 84% of the electricity generated comes from the burning of nonrenewable fossil fuels. Why are they referred to as nonrenewable? Fossil fuels were formed over millions of years to form. Scientists project that we’ll used up oil within a few decades. Coal and natural gas will last perhaps a few hundred years. Nature won’t renew them in time to continue supplying us with energy. Nuclear fuels will last less than 100 years.

Use of nonrenewable fuels has serious environmental consequences. Burning of fossil fuels produces the gas carbon dioxide, CO2. This contributes to the greenhouse effect and is responsible for the global warming now underway. The consequences of long-term global warming stagger the imagination. The effects on marine ecosystems will be profound. Rise in sea level will irrevocably alter coastal ecosytems. Dilution of sea water with fresh water due to melted icecaps will change the hydrology across broad swathes of ocean. Loss of reef habitats will reduce biodiversity and the ability of fisheries to recover from population declines.

Power stations also produce sulfur dioxide, which reacts with atmospheric water to create sulfuric acid. The resulting “acid rain” can kill entire habitats. Acid rain disrupts the water chemistry of aquatic ecosystems, adding nitrogen and phosphorus, thereby contributing to eutrophication.

Extraction of fossil fuels also incurs a high environmental cost. Many of the world’s remaining oil reserves are offshore. The BP oil spill in the Gulf of Mexico illustrated the risk associated with extracting these resources.

Thus, measures to reduce use of fossil fuels are desperately needed. At the same time, our dependence on fossil fuels has to end if we are to look forward to a sustainable future. Our best hope is renewable resources. Renewable resources will not run out. Sources include wind, geothermal, solar, hydroelectric and biomass energy. These sources have some impact on the environment, such as hydroelectric dams, which block rivers. On balance, the environmental impact of renewable resources is much less than that of nonrenewables.

Misconception Alerts
Highlight for students two misconceptions about use of electricity:

1. “Cars and trucks are the top consumers of fossil fuels and therefore producing the most CO2.” Not true, because of the use of fossil fuels to generate electricity, our daily use of electricity produces more CO2 than our use of cars. According to Energy Star “The average house is responsible for twice the greenhouse emissions than cars.”
2. “Converting energy from one form to another is efficient, so changing to energy efficient light bulbs and appliances will not make a difference.” Wrong! Every time energy is converted, heat is produced. This heat represents wasted energy. Each incandescent bulb produces nine parts of heat to make one part of light! Therefore switching to energy efficient devices could dramatically lower energy demand.

How we can improve energy efficiency
The best way to improve energy efficiency is to make simple changes to reduce the amount of electricity that we use. To demonstrate how easy it is to improve efficiency, provide with students the following examples. From these, students can see that just by changing light bulbs they can directly help to improve energy efficiency.

1. Replace older, full-size fluorescent lamps with newer, more efficient models. Fluorescent lighting is more efficient than incandescent lighting. However, many homes still use older fluorescent fixtures. By switching to new, full-sized fluorescent fixtures that are even more efficient, homes can improve their energy efficiency.
2. Replace incandescent lights with compact fluorescent lamps. Most homes use primarily incandescent bulbs for lighting. These bulbs heat a filament until it’s white hot to create light. Incandescent bulbs convert about 98 percent of the electricity to heat. Only 2 percent of the electricity goes to making light. Fluorescent bulbs on the other hand, convert about 10 percent of the electricity into light. Most incandescent fixtures can use compact fluorescent lamps (CFLs).
3. Use of LED lighting. Use of LEDs (light emitting diode) for domestic lighting is relatively new. LEDs work by passing current through a semiconductor material, which is stimulated to emit light. These bulbs are expensive but emit the least amount of heat. Currently available LEDs are at least three times as efficient as incandescent lighting. LED “solid state lighting” could halve the US’s energy use for lighting by 2025.
4. Install lighting controls. Light switches control lighting equipment in the home. Light switches are often left on when not in use. To reduce waste, timers and occupancy sensors will turn off lights when they’re not needed. Timers will turn off the lights after a set time interval. Timers work well in places, such as stairways, hallways, and closets, where use is intermittent and the space is occupied only for short periods.

(Adapted from http://www.pasolar.ncat.org/lesson01.php)

Pre-assessment survey

Have the students fill in the following knowledge survey on what they know about electricity. The guide is not to be graded and can be changed with answers adjusted as students learn more.

Anticipation guides are used for students to see how they have grown in their understanding of the concepts

It contains both correct and incorrect statements about the topic, students are then asked to agree or disagree. As they work through the lesson they take notes that verify or cause them to reconsider their original answer.

Directions: Before beginning the lesson ask students to complete the left column with Agree (A) or Disagree (D). Ongoing, encourage the student to collect information about each question. They then keep or change their answer in the final column. Print out the worksheet to hand to students.

Engage

1. Introduce students to the key concepts: heat, light, watts, lumens, energy, and electricity.
2. Ask students to individually brainstorm, a list of all of the ways they use lighting in their homes.
3. Show students different lightbulbs and explain the differences in how they work, and how much energy they use.
4. Have students compare answers to see the way lighting is most used in their home (e.g., lighting the living room while watching TV)
5. Have students look at the piechart below. Ask the following questions:
a. If each way to use electricity is a slice of pizza, and there are 10 slices altogether, how many slices go to lighting and appliances? (Answer = 2.5)
b. How could we reduce the amount of pizza going to lighting and appliances? (Answer: Use less light.)
c. But if you don’t want to watch TV in the dark (or other option from Step 4), what other option do you have? (Answer: Increase the efficiency of lighting.)
d. But how do you know which bulb is more efficient? (This is the hook to get students to perform the lab activity.)

See attached chart

Explain

1. Which bulb had the biggest difference between the start temperature and end temperature? Answer: the incandescent bulb
2. Which bulb had the highest end temperature? Answer: the incandescent bulb
3. Which bulb gave off the least heat? Answer: the compact fluorescent bulb
4. Which bulb appears to give off the brightest light? Answer: the higher wattage compact fluorescent and incandescent bulbs gave off about the same amount of light.
5. Which type of bulb is the most efficient? Answer: The most efficient bulb converts more energy to light and less to heat, therefore the compact fluorescent bulb is more efficient.
6. If electricity costs 1 cent per hour for each 100 watts of power, how much would it cost to run the bulb with the highest end temperature for an hour? Answer: Assuming the incandescent bulb is 100W, the cost is 1 cent (0.75 cents for a 75W bulb, etc.).
7. What is the difference in the hourly cost between the two bulbs? Answer: Assuming the CFL is 25W, the difference is 0.75 cents per hour (1 cent for the 100W – 0.25 cents for 25W)
8. If your home uses 20 of the bulbs with highest end temperature for 10 hours per day, what is the daily cost of running all the bulbs? Answer: Multiply out the cost by the number of bulbs and the time they’re used: 1 cent x 10 hours x 20 bulbs = 200 cents a day
9. If your home used 20 of the bulbs with lowest end temperature for 10 hours per day, what is the daily cost of running all the bulbs? Answer: Multiply out: 0.25 x 10 x 20 = 50 cents a day
10. What is the difference in cost per year in your home between using the bulbs with highest end temperature compared with the bulbs that have the lowest end temperature? Answer: Multiply the two daily costs by 365 and subtract: (200 x 365) – (50 x 365) = 73,000 - 18,250 = 54,750 cents = $547.50.
11. Say 1000 homes were in the same situation. What is the difference in cost per year for all the homes combined? Answer: Multiply answer from Step 9 by 1,000 = $547,500.
12. Assume it costs the town $500,000 to build a power station powered by fossil fuels to supply 1,000 homes. Now assume it costs $1,000,000 to build a power station powered by renewable energy to supply 1,000 homes. Using information from the above steps, what could people do so that the town could afford to build the power station using renewable energy? Answer: The difference in cost is $500,000. If everyone switched to the lower temperature light bulb, the difference in cost of electricity would pay for the renewable power station in two years.
13. Assuming the same information from question #9: 20 bulbs x 10 KWH/day x 365days/year x 1.325 lbs/KWH

Elaborate or extend

1. Show students the photograph below of the United States at night. Ask students: What does this photograph show them about the human population and our use of lights?
See attached image.
2. Show students the following video. http://www.youtube.com/watch?v=ibHXBCjttRU Ask students: Is wave energy a better source of power than fossil fuels? What are the advantages of wave power? What are its disadvantages? Explain your answer.

Evaluate

Have students return to the assessment survey to keep or change their answers and explain their responses in light of the evidence from the lesson. Discuss and write answers to the following questions

1. Summarize the advantages of incandescent bulbs for household use.
2. Summarize the advantages of CFL bulbs for household use.
3. What is the main benefit of widespread use of more efficient light bulbs?
4. Besides switching light bulbs, what other steps can you take at home to increase efficiency of energy use?

Standards

A. ESS Core Idea 4: Human activities are constrained by and, in turn, affect all other processes at Earth’s surface. [Human Interactions with Earth] Grades 6-8 ESS4.B: Natural Resources

Sub-question: How do humans depend upon Earth’s materials? Humans depend upon Earth for many different resources, including air, water, soil, rocks, minerals, metals, and sources of energy.

1. Where do we get the mineral and energy resources needed to construct and run our civilization?
• Humans depend on Earth’s land, ocean, and atmosphere for many different resources. Some of these resources are renewable over human lifetimes and some are non-renewable.
• Mineral resources are limited. Many are nonrenewable on human time scales and, at the present rates of usage; many will run critically low in the near future. Mineral resources are distributed unevenly around the planet, a result of how and where geologic processes have occurred in the past.
• Fossil fuels and uranium currently provide most of our energy resources.
• Fossil fuels like coal, oil, and natural gas are originally derived from solar energy, but take tens to hundreds of millions of years to form so are non-renewable on human time scales. They are likely to remain the dominant energy source for years to come, but they are becoming increasingly difficult to find and extract.
• Oil and natural gas are also used to make numerous products like plastics, textiles, medications, and fertilizers.
• Renewable energy resources such as solar, wind, hydroelectric, biomass, and geothermal, and the technologies to exploit them are being rapidly developed.

2. Why are soil and water considered to be limited resources when they are so common on Earth?

• Soil can take many thousands of years to form. Historically, much soil was lost as a result of human agricultural practices that amplify natural erosion processes. Modern soil conservation methods are increasing the protection and preservation Earth’s soil, but continual attention should be given this problem.
• There are vast amounts of water in the ocean, but humans cannot drink salt water. Only a small amount of Earth’s water is fresh, and humans get most of their water from streams, lakes, and groundwater. These sources are constantly renewed by rain and snow, but shortages arise when use exceeds supply or when fresh water is contaminated.

B. ESS Core Idea 4: Human activities are constrained by and, in turn, affect all other processes at Earth’s surface. [Human Interactions with Earth] Grades 6 – 8

ESS4.C Human Impacts on Earth

Sub-question: How do humans change the Earth?

Humans have become one of the most significant agents of geologic change at Earth’s surface. The activities that have built human civilizations have both positive and negative consequences related to the sustainability of these civilizations.

1. How do human activities alter Earth?

• Most actions that change the Earth's environments have both costs and benefits.
• Humans affect the quality, availability, and distribution of Earth’s water through the modification of streams, lakes, and groundwater. Pollution from sewage runoff, agricultural practices, and industrial processes can reduce water quality. Use of water for industry and agriculture may reduce drinking water availability.
• Large areas of land, including delicate ecosystems such as wetlands, are being transformed by human agriculture and land development.
• Human activities cause land erosion that exceeds all natural processes. These activities include plowing, urban construction, removal of vegetation, surface mining, and stream diversions, and increased rain acidity.
• Extraction of mineral resources and fossil fuels changes landscapes and often has significant side effects.
• Burning of fossil fuels has changed the fraction of carbon dioxide in the atmosphere significantly in the past 100 years.
• Human activities have significantly altered the biosphere, destroying many natural habitats and causing a huge decline in biodiversity.
• Modest changes in individual and societal activities can significantly reduce pollution.

Key Ideas

A. Most activities in everyday life involve one form of energy being transformed into another. For example, the chemical energy in gasoline is transformed into mechanical energy in an automobile engine. The use of energy has an impact on the Earth and its environment (eg. water, soil, organisms).
B. The use of different energy resources have different effects on the environment. An example is energy, in the form of heat, is almost always one of the products of energy transformations. There are global effects due to the byproducts of these energy transfers.
C. Since the Industrial Revolution, human activities have resulted in major pollution of air, water, and soil. Pollution has cumulative ecological effects such as acid rain, Global warming, or ozone depletion. The survival of living things on our planet depends on the conservation and protection of Earth’s resources.

See Student Resources and Student Worksheet pages attached.